diff --git a/src/core/state.ml b/src/core/state.ml
new file mode 100644
index 0000000..b017035
--- /dev/null
+++ b/src/core/state.ml
@@ -0,0 +1,9 @@
+(* State of the world, contains all the required information at any point *)
+type t = {
+  cartridge : option Cartridge.t;
+}
+
+(* Global reference *)
+let state = ref {
+  cartridge = None
+}